Stanford CoreNLP fornece NullPointerException
Estou tentando entender a API Stanford CoreNLP. Desejo que uma frase simples seja tokenizada usando o seguinte código:
Properties props = new Properties();
props.put("annotators", "tokenize");
StanfordCoreNLP pipeline = new StanfordCoreNLP(props);
// read some text in the text variable
String text = "I wish this code would run.";
// create an empty Annotation just with the given text
Annotation document = new Annotation(text);
// run all Annotators on this text
pipeline.annotate(document);
// these are all the sentences in this document
// a CoreMap is essentially a Map that uses class objects as keys and has values with custom types
List<CoreMap> sentences = document.get(SentencesAnnotation.class);
for(CoreMap sentence: sentences) {
// traversing the words in the current sentence
// a CoreLabel is a CoreMap with additional token-specific methods
for (CoreLabel token: sentence.get(TokensAnnotation.class)) {
// this is the text of the token
String word = token.get(TextAnnotation.class);
// this is the POS tag of the token
String pos = token.get(PartOfSpeechAnnotation.class);
// this is the NER label of the token
String ne = token.get(NamedEntityTagAnnotation.class);
}
// this is the parse tree of the current sentence
Tree tree = sentence.get(TreeAnnotation.class);
// this is the Stanford dependency graph of the current sentence
SemanticGraph dependencies = sentence.get(CollapsedCCProcessedDependenciesAnnotation.class);
}
// This is the coreference link graph
// Each chain stores a set of mentions that link to each other,
// along with a method for getting the most representative mention
// Both sentence and token offsets start at 1!
Map<Integer, CorefChain> graph = document.get(CorefChainAnnotation.class);
Isso foi retirado do próprio site da PNL de Stanford, então eu esperava que funcionasse imediatamente. Infelizmente isso não acontece, pois me fornece uma NullPointerException em:
for(CoreMap sentence: sentences) {...